大倾角大采高综采工作面煤壁非对称受载失稳特征

煤壁片帮是大倾角厚煤层综采亟待解决的关键问题之一,以2130煤矿25221大倾角大采高综采工作面为研究背景,采用理论分析、数值计算、物理相似材料模拟实验和现场监测相结合的综合研究方法,系统研究了大倾角大采高综采工作面煤壁的受载与失稳特征。结果表明,在大倾角大采高煤层开采中,受采高增大影响,围岩运动的幅度和剧烈程度较一般采高大倾角煤层开采时明显增大,覆岩垮落充填的非均匀特征进一步增强,煤壁支承压力的非对称特性亦明显增大;采动过程中煤壁的力学性质逐步劣化,伴随着裂隙的扩展、演化和贯通,煤壁开裂并形成滑移体,当滑移体周围约束解除或支承压力增大时,滑移体沿滑移面滑移,形成煤壁片帮;在工作面倾向,中部区域是煤壁片帮的高发区域,上部次之,下部最少,与煤壁的非对称受载特征相吻合;在垂直煤层方向,煤壁变形亦非对称,煤壁位移量中上部大于下部,靠近顶板区域易发生煤壁片帮;在煤壁重力倾向分量影响下,煤壁片帮易向倾向上部煤体蔓延。基于上述分析,并结合2130煤矿25221工作面的生产实际,提出了大倾角大采高综采工作面煤壁片帮防治措施。

Asymmetric load and instability characteristics of coal wall at large mining height fully-mechanized face in steeply dipping seam

The rib spalling is a technical problem to be solved urgently in steeply dipping thick seam mining.Based on the geological conditions and characteristics of strata behaviors at No.25221 working face in 2130 Coal Mine,the load and instability characteristics of coal wall is investigated by theoretical analysis,numerical simulation,physical analogue material simulation,and field monitoring.Results show that the asymmetry characteristics of mining pressure and strata behavior of large mining height face is higher than that of general mining height face in steeply dipping seam,which is due to mining height increase.Because the inhomogeneous characteristics of the overburden filling are further enhanced,the asymmetric characteristics of the supporting pressure of the coal wall are also obviously increased.During the process of mining,the mechanical properties of coal wall will gradually deteriorate,coal wall crazes and slip body appears.Then the slip body slides along the slip surface,rib spalling emerges,when the surrounding constraints of slip body are relieved or support pressure increases.In inclination direction,the central area is the high incidence area of rib spalling,upper secondary and lower minimum,which is consistent with the asymmetric loading characteristics of coal wall.Besides,in vertical direction,the displacement at the upper part of coal wall is larger than that at the lower part,and rib spalling is easy to occur near the roof area.And under the influence of the gravity tendency component of coal wall,the rib spalling is easy to spread to the upside.On the basis of safety production demands at No.25221 working face in 2130 Coal Mine,some control measures have been proposed in the paper.